Research Interests

My research program has been designed to investigate and understand what controls the atmosphere’s energy balance and how chemical reactions impact composition, pollutant and oxidant formation in the earth’s environment. Answers to these questions are highly relevant to understanding atmospheric climate change, as well as controlling air pollution and protecting public health.

My group has carried out a number of research projects to address important issues driving atmospheric radiative balance and chemistry with the support of NSF.

Demonstrated for the first time the existence of water vapor near UV absorption in the 290-350 nm region. Showed that water vapor near UV absorption can cause significant difference when laboratory water vapor absorption cross section data were used as input in modeling the solar flux at the ground level using a radiative transfer model.

Investigated adsorbed water UV absorption from monolayer to multilayer, and to heterogeneous nucleation. Demonstrated the sensitivity and the feasibility of Brewster angle cavity ring-down spectroscopy in studying molecular adsorption on surfaces at different coverage levels.

Measured wavelength-dependent UV absorption cross sections of surface-adsorbed HNO3 and surface-adsorbed H2O. Surface absorption cross sections of HNO3 and H2O are several orders of magnitude larger than those in the gas phase. Investigated nitric acid photolysis in the presence of water vapor. Demonstrated that this process does not directly lead to HONO production.

Discovered a new absorption band for nitrate on solid surfaces and determined for the first time nitrate near UV surface absorption cross sections. Provided molecular level understanding as to why nitrate photolysis rates on urban grimes, particles, and other surfaces are so much faster than those in the liquid phase.

Demonstrated the importance of gas phase photolysis of 2-nitrophenol and methyl-substituted 2-nitrophenols as missing OH and missing HONO sources in some polluted atmospheric environments. Illustrated why gas phase photolysis of 2-nitrophenols should be included in atmospheric models to close the gap in budgets of OH and HONO for the polluted atmosphere.